Light sensitive composition for photomagnetic printing process



Jan. 14, 1958 F. A. HAMM 7 2,819,963

LIGHT SENSITIVE COMPOSITION FOR PHOTOMAGNETIC PRINTING PROCESS Filed Jan. 7, 1955 GELATINO-S/LVER HAL/DE A EMULSION CONTAIN/N6 IRON v2; I Q

DEVELOPMENT & ETCH 14 I4 .F'ranklinA. Hamm IN VEN TOR.

' ATTORNEYS United States atentO LIGHT SENSITIVE COMPOSITION FOR PHOTO- MAGNETIC PRINTING PROCESS Franklin A. Hamm, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application January 7, 1955, Serial No. 480,489

7 Claims. (Cl. 96-94) entire thickness and the hardened portions will then adhere to the support upon washing with water. The unexposed portions will dissolve away and this process will yield a positive from a negative.

The material of my invention can be applied easily to most supports and can be processed in a simple manner. Its speed range is ideal for practical purposes, and it can be handled and coated in safe light. Other advantages of my process and material will be evident from the following description of my invention.

Accordingly, one object of my invention is to provide superior light-sensitive materials for making photographic resists which can be used as printing plates. Another object is to provide photographic resist materials which can be used for long periods of time without degradation of the printing surface. Still another object of my invention is to provide photographic resists which give a number of copies from the same printing surface, each of the copies being characterized by superior resolution and sharpness. Other objects will become apparent from a consideration of the following description and examples.

In practicing my invention, a ferromagnetic iron oxide, such as gamma ferric oxide (Fe O or ferroso-ferric oxide (Fe O is uniformly dispersed in a photographic 'gelatino-silver-halide emulsion and the mixture is coated uniformly on a surface. The photographic emulsion is then exposed in the usual manner and processed to a relief image. The relief image is then magnetized or sensed, developed with finely divided iron (ferromagnetic) and copies obtained by contact transfer printing, for example. Although a relief or resist image is formed in the silverhalide emulsion layer, it is the magnetic property of the iron oxides which is the important aspect in the'production of copies from the master. The quality of the master is not impaired by light, heat, moisture, or pressure. The .magnetism' is not inadvertently erased.

In the accompanying drawing, the various figures show in enlarged cross-sectional view the structure of a representative sensitive element of my invention at various stages in the process of producing printing plates having select areas covered by the resist images.

The quantity of ferromagnetic iron oxide dispersed in the photographic silver-halide emulsion layer can be varied, depending upon the type of copy which is to be produced. The optimum quantity for a given purpose can be ascertained by making a series of test strips containing various quantities of ferromagnetic oxide. In genods of processing are discussed in detail below. Other methods of obtaining a relief image can also be employed, depending upon the use to which the relief image is to be put. 2

The relief image thus formed is magnetized or sensed using a recording head so that the relief image is now also a magnetic image. This magnetization can be accomplished in known manner, at various A. C. frequencies and speeds of motion of the magnetic matrix. However, the condition of 250 cycles/second, 8 volts, milliamperes, and a speed of about 2-3 inches per second has proved to be very satisfactory. Contact recording (sensing) is desirable. Other methods of magnetizingthe relief record can be employed equally well. Such methods of magnetization are matters of common knowledge.

The magnetic latent image thus obtained is then developed to a magnetic visible image using finely divided iron (ferromagnetic). A suspension of this free iron (sometimes referred to as a magnetic ink) in carbon tetrachloride or other vehicle can be flooded over the relief image, or the master image can be immersed in the suspension. In both cases, the magnetic lines of force in the magnetized relief image attract the soft iron (ferromagnetic) particles and hold them firmly in contact with the relief image. Regions in the master which are void of the ferromagnetic iron oxide matrix are free of developing iron. Also, the amount of iron attracted to regions in the relief image will be somewhat dependent on the thickness of the image at any given region.

Copies can best be made by contact transfer. One method comprises using a moist, pressure-sensitive adhesive transfer material, such as dye transfer paper. The dye transfer paper is slightly moistened on the gelatin side and this side is placed in contact with the developed master. Gentle pressure results in transfer of the iron from the surface of the master matrix to the gelatin surface of the dye transfer paper. There is thus obtained an image on the transfer paper which consists of free iron embedded in gelatin. The record thus obtained can be preserved by spraying with a solution of an organic solvent containing dissolved resin, such as polymethyl methacrylate, polymethyl acrylate, etc.

Alternatively, transfer of the image from the resist material to a desired surface can be accomplished by placing the master image in contact with dry dye transfer paper with the gelatin coating thereof in contact with the developed master. When dry heat is applied to the rear surface of the dye transfer paper, transfer of the iron from the master surface occurs. A heat-sealing iron can also be used.

The following example will serve to illustrate further the manner of practicing my invention.

EXAMPLE Six parts by weight of gamma ferric oxide were mixed with about 4 parts by weight of a photographic gelatinosilver-halide emulsion and the dispersion coated on a 'photographic support, suchas cellulose acetate.

(a) Tanning development A photographic element obtained as described above was exposed to a line image through the base. The exposed emulsion layer was then developed for two minutes in a tanning developer of the type described in John .UgS. Patent 1,482,613, issued February 5, 1924 (see page 2, column 2, lines 2535). Following development, the emulsion was subjected toza 3-minute wash in running .water at. 140 .F. 7

\ (b) Regu-lardeve-lopment A second photographic.,element.wasvmade as described aboveand exposed to a line image in the.conventional waythrough the photographic emulsionlayerfinstead of 'thebase. Theexposedemulsion layer wasthen'developed for 4 minutes in Kodak'Developer D 19. The developed .emulsion was then fixed and washed in the usual manner.

The emulsion. layer was then subjectedfor 45 seconds .toan etch=bleachbath .of the'following composition:

Part A:

:Cupric nitrate grams .200 Potassium bromide do .10 Glacial acetic acid "cc..- -160 Water to make 1 liter. Part B: 3 hydrogen peroxide solution.

Equal parts by volume of A and Babove were mixed immediately before use.

Afterthe silver emulsion was completely bleached by the above solution,'the outer surface ofthe element was gently washed with water and the resulting relief image allowed. to dry.

() Making copies The relief image which had beenobtained 111113311; a (or partb) above was sensed magnetically by passing the reliefimage past a magnetic recordinghead which had .been'positioned in the chuck of a milling machine. The

table speed was 2.5 inches per second and the length of the air gap in the recording head was 1.96 mils. The "gap width was about 0.75 mil. The displacement normal .to the motion of the milling machine was indexed to 150 mils so that an overlap of 46 mils occurred during each track length. In order to avoid white separation lines in the printed copies,,it was found that the length of the magneticrecording head should be'made approximately 'equalto the width of the area tobezmagnetized. Magnetic erasure is thus avoided.

The resist imagewhich had thus been magnetically sensed was then treated with powiderediron (ferromagnetic) as described above. Carbonyl Iron, Type G, sold .by'the General Aniline and FilmCorporation was found :tozbe nseful asgthe fdeveloping: iron. It was found to be about 98%. :,pure..and2 tohave a weight-average. diameter :of.about:8: microns. A'ItlWfiS: spherical inform. The de veloped imagewasthenplaced in .contact with dye transfer; paper and. an image not" excellent resolution obtained.

[.Sinceexposureiszgenerallyrmadeithrough the base or support when a tanning developmentis employed, thev image obtained is.-a.negative.of the-'originallimage and its lefterightrdirections.are;reversedwith respect to the origirnal. :When. the;regu1ar development andetch-bleach treatsmenteare employed, .thevexposure is .from the emulsion :side,5and the copy is apositive of :the original andhas .correcttorientation.

The process .of my invention .is most advantageously suited for line copies. If desired, copies can be made .of an original by exposurelinta camera in the ordinary manner or exposure .can be made through a-negativeor positive in the usual manner. The quality of the copies can be improved somewhat in those cases where transferis affected to a'support having thereon a gelatin layer *by' applying slight pressure tothe rear side of the support having thereon the.gelatin.layer. =While the above example employed a photographic gelatino-silver-halide emulsion wherein thehalide was bromiodide, other silver -Kodak potassium bromide do halides can be employed to advantage, such as the ordinarily employed gelatino-silver-chloride, gelatino-silverbromide, gelatino-silver -;chlorobromide, gelatino-silverbromiodide, etc. emulsions.

Kodak sodium carbonate, monohydrated do 52.5 5.0 Cold water to make 1.0 liter.

My invention can be further illustrated by reference to the accompanying drawing. Figure 1. shows a support 10 of any suitable material, such as cellulose acetate, polyvinyl acetal, etc., coated with a layer 11 containing a photographic gelatino-silver-halide emulsion havingdispersed therethrough a ferromagnetic, iron, oxide, such .asgamma ferric oxide. In Figure 2 the light-sensitive material shown in Figure lhas been exposed to'light under an image having transparent portions :13 and opaque portions'12. After developmentof the exposed element shown in Figure 2 and treatment with an etch-bleach bath as-shown above, there is obtained the resist image shown in Figure 3. The image consists of raised portions 14c0ntaining gamma ferricoxide or otherferromagnetic material. This resist image can then be magnetized as described above and the magnetized. surface treated with iron powder to produce a visible recorddf .the subject. 'This visible record can then. be transferred to another surface, such as dye ,transfer paperjis'described in detail above.

What I claim as my invention and desire secured by Letters Patent of the United States is:

1. A photomechanical resist composition comprisinga photographic gelatino-silver-halide emulsion and afferromagnetic iron oxide.

'2. A photomechanical resist composition comprising a photographic, gelatino-silverahalide. emulsion and gamma ferric oxide.

.3. A photomechanical resist compositioncomprisinga photographic gelatino-silver-bromiodide emulsion and gamma ferric oxide.

4. Aphotographic'element comprisingta support having thereon a layer comprising a photographic gelatinosilver-halide emulsionand a ferromagnetic iron oxide.

"References'Cited in the file of this patent UNITED STATES. PATENTS 494,526 Forster Mar. 28, 1893 1,213g 'Bullis Jan. 23,1917 2,500,052 Yackel Mar. 7,1950 2,657,932 Blaney Nov. 3,1953

OTHER REFERENCES Journal of .The- Franklin: Institute, November 1951,: vol. 252, No. 5, pp. 373.to 38,1. .-(.Copy:in Div. .17.)

General Electric Review, July/1952, vol. 55, No. 4,

PP- 120,121, 22:and 61. (CopyxinDiv. 17.) 

1. A PHOTOMECHANICAL RESIST COMPOSITION COMPRISING A PHOTOGRAPHIC GELATINO-SILVER-HALIDE EMULSION AND A FERROMAGNETIC IRON OXIDE. 